Scrolling of dvi files has improved lately, but still lags behind that of v5; in particular, it is coarse initially, and becomes finer after hitting 'u', 'd' keys.

Sometimes the viewer opens up with the page displaced deep into the lower right corner of screen.

In Editor, you might wish to add completions for \begin{document}, \end{document}, and, if possible, offer a few more colorization options (e.g., for curly and square braces, text-math and display-math environments; the '&' array column separator).